[flyingfrizzle]

Rich 10, I moved your new post here to your original one since it was basically the same question with more information added to it. Trying to keep from having multiple threads with the same question filling the form. Plus you will get better responses keeping all the info in one thread so people can gauge what has been said and add to it.

I will add this and maybe it will help you out a little bit more on selecting a prop.

Im not really sure what you are asking but I am thinking you want prop suggestions for an Yamaha 150 or 175 to make sure you can get 40-45 mph out of it? Just odd due most people prop their boat looking at other conditions and speed is usually the last thing people worry about except for efficiency. Between different props you may see a 5-7 mph difference but not as much as you would think.

Far as pitch, you will pick this based on the rpm range on your outboard. You want the rpms at wide open throttle with a normal load on the boat to rev to the max recommended rpms of the outboard at least. If not slightly over the max recommended rpm this way if your loaded down more you will not lug the motor. I don't know what people run on their 4 stroke Yamahas but I would guess start with a 17p or 19p and go up or down from there to match your rpms to the prop pitch. Some one with a Yamaha can get you close pitch recommendation for you to start with. Far as diameter I would stay small if you are concerned about mph and getting in the 40-45 mph range. Some where around 14 1/2" or so. The larger 15" plus props will handle and bite the water better but slow you down speed wise. I would try a old model mercury vengeance prop, not a expensive prop but a good smaller dia prop that will give you a base line to start from. It will fit your Yamaha. The Yamaha salt water II props are good as well. You can buy or borrow one to try it out first and tune from there. The mercury fury or any of the newer props made from the x7 alloy can be faster than the standard ss models due to their lighter thinner blades. The new alloy makes them strong enough to lighten them up. If your man concern is about is getting the mph up you can work on dialing in your motor height. Raise the outboard as high as possible with out slipping the prop and get the av plate slightly out of the water. This will reduce drag and add more mph than a prop change most times.

It may be best if you ask or research the form and look at hulls like yours with the Yamaha 150 - 175s and see what they were running far as props and what there posted performance numbers were. You may can get a good idea what to expect from this combination. That will probably help you the most picking an prop to go on yours.